One of the four bases in DNA that make up the letters ATGC, adenine is the "A". The others are guanine, cytosine, and thymine. Adenine always pairs with thymine. See alsoprotein, nucleotide, uracil, thymine, guanine

A group of DNA containing viruses which cause respiratory disease, including one form of the common cold. Adenoviruses can also be genetically modified and used in gene therapy to treat cystic fibrosis, cancer, and potentially other diseases. See alsocancer

A technique used in model organism studies in which embryos at the 8-cell stage of development are pushed together to yield a single embryo (used as an alternative to microinjection). See also: model organisms

A rare inherited liver disorder seen in infants and young children. The disease is characterized by a buildup of bile in the liver due to a deficiency or absence of normal bile ducts inside the liver and a narrowing of bile ducts outside the liver. Symptoms of the disorder can include jaundice, stunted growth, fatty deposits in the skin, facial deformities, and abnormalities in the heart, eyes, vertebrae, and kidneys. See alsogene, inherited

One of the variant forms of a gene at a particular locus, or location, on a chromosome. Different alleles produce variation in inherited characteristics such as hair color or blood type. In an individual, one form of the allele (the dominant one) may be expressed more than another form (the recessive one). See alsochromosome, deletion, dominant, gene, insertion, locus, recessive, substitution

Modern Language Association (MLA)

Alternative form of a genetic locus; a single allele for each locus is inherited from each parent (e.g., at a locus for eye color the allele might result in blue or brown eyes). See also: locus, gene expression

A laboratory animal useful for medical research because it has specific characteristics that resemble a human disease or disorder. Scientists can create animal models, usually laboratory mice, by transferring new genes into them. See alsogene, deletion, mutation, transgenic

A blood protein that is produced in response to and counteracts an antigen. Antibodies are produced in response to disease and help the body fight against the particular disease. In this way, antibodies help the body develop an immunity to disease. See alsolymphocyte, protein

Each generation of offspring has increased severity of a genetic disorder; e.g., a grandchild may have earlier onset and more severe symptoms than the parent, who had earlier onset than the grandparent. See also: additive genetic effects, complex trait